We have initiated studies to evaluate the possible involvement of viruses in the etiology and pathogenesis of a variety of eye diseases such as retinal degeneration and uveitis. We have also continued our stludies on lymphokines and regulatory cells in retinal degenerative disorders. Retinitis pigmentosa is a group of diseases of unknown etiology which is characterized by degeneration of the retina and the associated retinal pigment epithelial cell. The pathophysiologic processes involved in the maintenance of retinal integrity is only partly understood and the processes involved in retinal degenerations are not known. We have identified an abnormality in a regulatory protein (interferon-gamma) and an altered expression of a cell surface antigen (HLA-DR) in this disease. These data point to the possibility of an underlying abnormality in biologic control mechanisms in retinitis pigmentosa.